US4908172A - Production of ceramic moldings - Google Patents

Production of ceramic moldings Download PDF

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Publication number
US4908172A
US4908172A US07/220,176 US22017688A US4908172A US 4908172 A US4908172 A US 4908172A US 22017688 A US22017688 A US 22017688A US 4908172 A US4908172 A US 4908172A
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Prior art keywords
solvent
mold
molding
mixture
molecular weight
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Expired - Fee Related
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US07/220,176
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English (en)
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Hans-Josef Sterzel
Gunther Mair
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BASF SE
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BASF SE
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Assigned to BASF AKTIENGESELLSCHAFT reassignment BASF AKTIENGESELLSCHAFT ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: MAIR, GUNTHER, STERZEL, HANS-JOSEF
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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/63—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B using additives specially adapted for forming the products, e.g.. binder binders
    • C04B35/638—Removal thereof
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/63—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B using additives specially adapted for forming the products, e.g.. binder binders
    • C04B35/632—Organic additives
    • C04B35/634—Polymers
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/63—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B using additives specially adapted for forming the products, e.g.. binder binders
    • C04B35/632—Organic additives
    • C04B35/634—Polymers
    • C04B35/63404—Polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • C04B35/63408—Polyalkenes

Definitions

  • the present invention relates to a process for the production of ceramic moldings, in which a ceramic powder is mixed with a molding additive, the mixture is injected into a mold which determines the final shape and dimensions of the molding, the molding additive is removed and the molding material is sintered.
  • the present invention starts from a known process described in EP-A-O No. 125 912, which has been used to date for the production of ceramic moldings by injection molding.
  • a ceramic powder is mixed with a thermoplastic, wax or a lubricant, such as stearic acid or oleic acid, and the mixture is granulated.
  • the granules are converted into a green compact by means of an injection molding machine.
  • the granules to be plasticized act like a lubricting gel paste in the injection molding machine and, particularly in the melting zone where the material is not yet sufficiently plasticized, remove metal chips from the machine parts, which chips cannot be removed from the green compact.
  • the metal particles lead to inhomogeneities in the sintered molding and adversely affect its mechanical properties.
  • the high shear rate in the injection nozzle and in the mold cores results in a high degree of orientation of the polymers required as fluxes, which may lead to mechanical stresses in the molding and hence to the formation of microcracks.
  • Microcracks often remain after subsequent removal of the organic additives by baking and after sintering and also substantially reduce the reliability and strength of the sintered moldings.
  • Another disadvantage is that the organic molding additives used have to be removed completely from the green compact by pyrolysis before the actual sintering process. Pyrolysis, also known as baking, must be carried out sufficiently slowly to prevent the pressure of the escaping gases from causing additional cracking and pore formation, i.e. the gases must be able to diffuse through the green compact without substantial pressure build-up. This requires pyrolysis times which are, for example, as long as several days in the case of wall thicknesses of only 2-4 mm and hence greatly reduce the cost-efficiency of the process.
  • the molding additive used is a solution of a high molecular weight polymer in a solvent, about 50-80% by volume of the agglomerated ceramic powder being mixed with about 50-20% by volume of the solution and the mixture being injected at a temperature below the boiling point of the solvent and under from 100 to 1,500 bar into a porous, gas-permeable mold which is at a temperature above the boiling point of the solvent, and when the injection pressure is maintained until gas no longer escapes from the molding material or from the mold.
  • a ceramic powder is mixed with a molding additive, in particular a high molecular weight polymer, dissolved in a solvent.
  • the volume ratio of ceramic powder to solution is from about 1:1 to 1:4.
  • Suitable solvents for the high molecular weight polymers are water, alcohols, such as ethanol, n-propanol or isopropanol, and nonpolar solvents, such as aliphatic hydrocarbons.
  • Oxide ceramic powders for example magnesium oxide, alumina, mullite, zirconium oxide or spinel, are most advantageously deagglomerated in water, so that water is advantageously used as a solvent for processing them. Accordingly, water-soluble polymers are used to increase the viscosity.
  • high molecular weight water-soluble polymers When dissolved in water, high molecular weight water-soluble polymers form highly viscous solutions having viscosities of from 100 to 10,000 dPa.s at concentrations as low as from 0.05 to 1% by weight. Hence, these aqueous solutions possess, at room temperature, viscosities which correspond to the viscosities at 150°-300° C. of the polymers usually used as fluxes. Because of the high viscosity, the suspension of the ceramic powder is stabilized, and separation does not occur even under high shear gradients. The hydrostatic forces which occurred during injection are transmitted to the individual powder particles.
  • suitable water-soluble polymers are polyvinylpyrrolidone, polyacrylic acid and its salts, polymethacrylic acid and its salts, polyvinyl alcohol, polyacrylamide and copolymers of monomers of the stated polymers.
  • Other comonomers are dimethylaminoethyl acrylate methochloride and diethylaminoethyl acrylate sulfate.
  • the weight average molecular weight of the water-soluble polymers is from 1 to 10 million g/mole.
  • Such polymers and copolymers are commercially available and are used as thickeners, as fluxes for reducing the resistance to flow and as precipitation assistants.
  • Nonionic polyacrylamides which contain small amounts of polyacrylic acid are preferably used as nonanionic polymers having molecular weights of from 3 to 10 million g/mole.
  • Anionic water-soluble polymers are copolymers of acrylamide with 20-70% by weight of ammonium acrylate, having molecular weights of from 5 to 10 million g/mole. Since alkali metal cations have an adverse effect on particle boundary growth during sintering of the ceramic powder, ammonium ions are preferred as counter-ions.
  • Cationic water-soluble polymers are polyacrylamides which contain from 30 to 80% by weight of dimethylaminoethyl acrylate methochloride or diethylaminoethyl acrylate sulfate and have molecular weights of from 3 to 5 million g/mole.
  • Water-soluble high molecular weight natural polymers and their derivatives such as alginates, methyl/ethyl- or carboxymethylcellulose, starch or ligninsulfonates, can also be used.
  • Water-soluble polymers which can particularly preferably used are those which are slightly crosslinked with 50 to 1,000 ppm of polyfunctional crosslinking agents, such as diacrylyl or dimethylacyl compounds. Such polymers consist mainly of ammonium acrylate and acrylamide. They are usually used as printing ink thickeners for textile printing. Compared with the completely uncrosslinked water-soluble polymers, they have the advantage that higher viscosities can be obtained at low concentrations, for example about 10,000 dPa.s at a shear gradient of 0 and at room temperature with a 0.2% strength aqueous solution. In addition, they have very little tendency to flocculate the ceramic powders.
  • the concentrations to be used depend on the desired viscosity and on the molecular weight; however, they should not exceed 0.2% by weight, based on the ceramic material.
  • the type of surface charge on the ceramic powder must be determined. It is essential to avoid a situation where the charges on the polymer have the opposite sign to the surface charge on the ceramic powder. In this case, undesired coagulation of the powder would occur. It is for this reason that the use of the slightly crosslinked water-soluble polymers with their low tendency to coagulation is particularly preferred.
  • the organic material volatilizes during heating in the sintering process.
  • the material required for production of the ceramic moldings by injection molding is prepared by deagglomerating the ceramic powder by milling in fully demineralised water, with or without the addition of small amounts of a surfactant.
  • the final amount of water, i.e. from 20 to 50% by volume, is used from the outset.
  • the suspension is transferred to a kneader and the water-soluble polymer is added. Kneading is carried out until the polymer has completely dissolved and the viscosity is constant, which is recognizable from the power consumption of the kneader.
  • non-oxide ceramic powders of silicon nitride, silicon carbide, sialones and other non-oxide materials dispersing in water is in principle also suitable.
  • non-oxide powders can be more readily deagglomerated in nonaqueous solvents.
  • the long residence time in water in the case of hydrolyzable materials, such as silicon nitride may lead to the formation of undesirable oxide layers at the powder surface or increase the existing oxygen content in an uncontrollable manner.
  • a nonaqueous solvent/polymer system is suitable for such ceramic powders.
  • the abovementioned water-soluble polymers are also soluble in alcohols, provided that no more than 5 mol % of the polymers are present as salts (ammonium polycarboxylates or polyammonium salts).
  • the high molecular weight polymers to be employed should be matched in their solubility with the said solvents.
  • high molecular weight polystyrene is soluble in aromatic hydrocarbons, such as toluene or xylene.
  • the aliphatic hydrocarbons such as hexane, heptane or, in general, petroleum ethers and gasoline fractions, are particularly preferred dispersants for non-oxide ceramic powders.
  • polyisobutylene having a molecular weight of 5 million g/mole or more is particularly suitable.
  • polyisobutylene does not form a carbon residue during pyrolysis, so that the stoichiometric ratios in the subsequent sintering process are not adversely affected.
  • the mold wall preferably consists of an open-pore sintered metal whose surface roughness is reduced to 0.5-2 ⁇ m by flame spraying or plasma spraying with a very finely divided metal powder, metal oxide powder, such as Cr 2 O 3 or ceramic powder, such as boron nitride. In addition to low surface roughness, this results in good mold release properties, especially in the case of boron nitride.
  • the sintered metal layer is kept very thin, i.e. about 1-10 mm. Adjacent to this is compact mold material which, for removal of the vapors, is provided with holes which lead to the sintered metal layer. The stream or the organic vapor is removed centrally from the mold, which is gas-tight to the outside, into a condensation apparatus.
  • the mold is, for example, electrically heatable by means of heating elements.
  • the novel process permits the preparation of stable suspensions of nonagglomerated ceramic powders. Because evaporation of the solvent takes place under an opposing pressure which is far greater than its vapor pressure, neither pores nor cracks can form in the mold.
  • the temperature of the mold wall is in general from 150° to 450° C., preferably from 200° to 400° C.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Ceramic Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Producing Shaped Articles From Materials (AREA)
  • Compositions Of Oxide Ceramics (AREA)
US07/220,176 1987-07-29 1988-07-18 Production of ceramic moldings Expired - Fee Related US4908172A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19873725138 DE3725138A1 (de) 1987-07-29 1987-07-29 Verfahren zur herstellung keramischer formteile
DE3725138 1987-07-29

Publications (1)

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US4908172A true US4908172A (en) 1990-03-13

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US (1) US4908172A (de)
EP (1) EP0301408A1 (de)
JP (1) JPS6442205A (de)
DE (1) DE3725138A1 (de)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5209885A (en) * 1991-06-28 1993-05-11 W. R. Grace & Co.-Conn. Aqueous extrusion of silicon nitride
US5248457A (en) * 1992-01-21 1993-09-28 Megamet Industries Method for producing intricately shaped particulate bearing precursor components with controlled porosity and density
US5356578A (en) * 1988-08-08 1994-10-18 Kawasaki Steel Corporation Mold for slip casting and method of slip casting
US5417756A (en) * 1992-11-25 1995-05-23 Hoechst Aktiengesellschaft Process and molding compound for producing inorganic sintered products by injection molding
GB2291830A (en) * 1994-08-02 1996-02-07 Dytech Corp Ltd Moulding ceramic articles
US5900201A (en) * 1997-09-16 1999-05-04 Eastman Kodak Company Binder coagulation casting
US5989492A (en) * 1994-12-19 1999-11-23 Aga Aktiebolag Process including heating and cooling for production of an injection-moulded body
US6203638B1 (en) * 1992-06-02 2001-03-20 Certech, Inc. Method of making injection molded ceramic cup
US20070144544A1 (en) * 2005-09-30 2007-06-28 Cai David J Oral composition and method for stress reduction associated with smoking cessation
US20080232996A1 (en) * 2007-03-22 2008-09-25 Commissariat A L'energie Atomique Method for Fabricating Parts by PIM or MICROPIM
US20100162771A1 (en) * 2008-12-31 2010-07-01 Zircoa, Inc Method of forming ceramic strings and fibers
CN113458398A (zh) * 2021-06-09 2021-10-01 北京科技大学 一种注射浆料实现金属注射成形的方法

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2649093B1 (fr) * 1989-06-30 1991-09-13 Comp Generale Electricite Procede de mise en forme d'une ceramique supraconductrice
JP4688334B2 (ja) * 2001-04-09 2011-05-25 ニチロ工業株式会社 梱包用バンドリール
DE102010007780A1 (de) * 2010-02-12 2011-08-18 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V., 80686 Spritzgießverfahren für Kondensationsharze und Vorrichtung für das Verfahren

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4113480A (en) * 1976-12-09 1978-09-12 Cabot Corporation Method of injection molding powder metal parts
EP0125912A1 (de) * 1983-05-13 1984-11-21 Ngk Insulators, Ltd. Verfahren zur Herstellung von keramischen Formteilen
US4734237A (en) * 1986-05-15 1988-03-29 Allied Corporation Process for injection molding ceramic composition employing an agaroid gell-forming material to add green strength to a preform

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1093280B (de) * 1959-04-15 1960-11-17 Beru Werk Ruprecht Gmbh Co A Verfahren zur Herstellung von keramischen Koerpern fuer Zuendkerzen und Zuendkerzenanschlussteile
DE1771643B2 (de) * 1968-06-20 1973-10-31 Porzellanfabrik C.M. Hutschenreuther Arzberg, Zweigniederlassung Der Hutschenreuther Ag, 8594 Arzberg Verfahren zur Herstellung keramischer Formlinge und Spritzpreßform zur Durch fuhrung des Verfahrens
JPS5927743B2 (ja) * 1979-02-28 1984-07-07 旭硝子株式会社 セラミック紛未の成形品の処理方法
ATE42534T1 (de) * 1985-09-26 1989-05-15 Studiecentrum Kernenergi Verfahren zur herstellung eines gesinterten formkoerpers.

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4113480A (en) * 1976-12-09 1978-09-12 Cabot Corporation Method of injection molding powder metal parts
EP0125912A1 (de) * 1983-05-13 1984-11-21 Ngk Insulators, Ltd. Verfahren zur Herstellung von keramischen Formteilen
US4734237A (en) * 1986-05-15 1988-03-29 Allied Corporation Process for injection molding ceramic composition employing an agaroid gell-forming material to add green strength to a preform

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5356578A (en) * 1988-08-08 1994-10-18 Kawasaki Steel Corporation Mold for slip casting and method of slip casting
US5209885A (en) * 1991-06-28 1993-05-11 W. R. Grace & Co.-Conn. Aqueous extrusion of silicon nitride
US5248457A (en) * 1992-01-21 1993-09-28 Megamet Industries Method for producing intricately shaped particulate bearing precursor components with controlled porosity and density
US6203638B1 (en) * 1992-06-02 2001-03-20 Certech, Inc. Method of making injection molded ceramic cup
US5417756A (en) * 1992-11-25 1995-05-23 Hoechst Aktiengesellschaft Process and molding compound for producing inorganic sintered products by injection molding
GB2291830A (en) * 1994-08-02 1996-02-07 Dytech Corp Ltd Moulding ceramic articles
GB2291830B (en) * 1994-08-02 1998-10-21 Dytech Corp Ltd Manufacture of ceramic articles
US5922272A (en) * 1994-08-02 1999-07-13 Dytech Corporation Limited Manufacture of ceramic articles
US5989492A (en) * 1994-12-19 1999-11-23 Aga Aktiebolag Process including heating and cooling for production of an injection-moulded body
US5900201A (en) * 1997-09-16 1999-05-04 Eastman Kodak Company Binder coagulation casting
US6065195A (en) * 1997-09-16 2000-05-23 Eastman Kodak Company Method of manufacturing inkjet print head base elements by sacrificial molding
US20070144544A1 (en) * 2005-09-30 2007-06-28 Cai David J Oral composition and method for stress reduction associated with smoking cessation
US20080232996A1 (en) * 2007-03-22 2008-09-25 Commissariat A L'energie Atomique Method for Fabricating Parts by PIM or MICROPIM
US20100162771A1 (en) * 2008-12-31 2010-07-01 Zircoa, Inc Method of forming ceramic strings and fibers
CN113458398A (zh) * 2021-06-09 2021-10-01 北京科技大学 一种注射浆料实现金属注射成形的方法

Also Published As

Publication number Publication date
DE3725138A1 (de) 1989-02-09
JPS6442205A (en) 1989-02-14
EP0301408A1 (de) 1989-02-01

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